Cataract refers to a medical deficiency of the eye due to loss of transparency of the crystalline lens. An accepted treatment for this condition is surgical removal of the crystalline lens and replacement by an artificial intraocular lens.
Multicomponent intraocular lenses (MC-IOL) for use in refractive cataract surgery are known in the art as illustrated e.g. by publications WO-A-2008094518, WO-A-2011006008 and WO-A-2012054854. A multicomponent intraocular lens includes a base component suitable for posterior chamber implantation and at least one front component that is detachably attached to the base component and that can be modified by either exchanging the front component or by altering the refractive properties in vivo at any post-operative time. The above-described structure permits the base component to form a platform upon which the at least one front component is placed and attached in a releasable manner. During routine cataract surgery, the MC-IOL replaces the crystalline lens of the human eye. Once a patient's eye has healed after such a surgery, the surgeon reenters the eye and modifies or replaces the front component, if necessary, to modify the optical characteristics of the eye until the desired levels for each optical characteristic are attained.
MC-IOLs that are designed specifically to permit the easy exchange of front optical components at a post-operative period involve considerable benefits in terms of visual correction. This is because the actual surgery of implanting the lens in the first place, as well as variances in the manner in which the eye heals after implantation, potentially create distortions which may not stabilize for several months after the operation. Therefore, the ability to measure and to compensate for the distortions optimally takes place several months after surgery and cannot typically be predicted prior thereto. Since the same surgical wound may be used for both the primary and secondary operations, additional distortion due to wound healing would not be anticipated as a result of the second operation. Furthermore, the ability to exchange optical components of a multicomponent intraocular lens can be economical compared to removing, modifying, and re-implanting a single component lens, as well as easier to perform.
The MC-IOL concept allows for adjustments or enhancement operations, beyond its use in primary cataract surgery to compensate for any miscalculation or any biological variability or any change in the condition of the eye over time after the primary operation. In order for these surgical adjustments to be workable, the surgeon must have easy access to the front component. To assure this, the front component must be left out of the capsule, in the sulcus. On the other hand, the base component is left in the capsule.
In a prior art MC-IOL, the edges of the capsule are placed between the haptics of a front lens assembly and an underlying base lens. Vertically extending flanges of the base lens and their corresponding slots allow a space between the haptics of the front lens assembly and the base lens, so that a special instrument, referred to as a capsule snare, allows the surgeon to place the front lens assembly haptic above the edges of the capsule. The vertically extending flanges and corresponding slots position the front lens assembly in front of or away from the capsule, that is, in the sulcus, making surgical removal and replacement of the front lens assembly very safe and technically simple. Put another way, the flanges and slots assure easy removal and replacement of the front lens assembly during an enhancement operation, despite the normal healing process that involves capsule contracture around the base component.
DE-U-202013009162 discloses an intraocular lens assembly comprising an intraocular lens structure for implantation in a capsular bag of an eye. The IOL comprises an optical structure having a periphery, at least two rear supports connected to the periphery and extend away therefrom, intended to be within the capsular bag when the IOL is implanted in the capsular bag, and at least two front legs connected to the periphery of the optical structure and extend away therefrom, intended to be located outside of the capsular bag. The front legs and the rear supports hold a front capsular bag between them. In an embodiment, the intraocular lens assembly further comprises a secondary intraocular lens for attachment to a front side of the IOL. The S-IOL comprises a secondary optical structure 35 and at least two fixing portions 37 each of which is intended to cooperate with one of the said front supports 8 to secure the S IOL to the IOL. In an embodiment, the capsular bag can be clamped between a front surface of the rear supports and a rear surface of the fixing portions 37.
The primary problem of this configuration is the difficulty or impossibility to rotate the lenses combination once they are assembled together because the tabs have captured the capsule edge and cannot be easily disengaged. Indeed, in case of a toric correction, orientation is determined and must be modified by the surgeon in the eye of the patient during surgery by rotating the elements inside the capsular bag when both lenses are assembled together. When assembled together, the system of DE-U-202013009162 will create a tension on the capsulorhexis which may prevent lens rotation, and thus, not allowing for proper axis orientation. In other words, it is not possible to manipulate such lens system inside the capsular bag to properly orient the lens axis.